The invention relates to a method for the coupling of articulated track links with a determined tolerance by means of press fitting.
The invention also relates to an apparatus specifically aimed at performing the above-named method.
In particular, but not exclusively, said method is applied in the coupling of articulated link track chains for tracker vehicles. Such track chains normally comprise a plurality of links having reciprocally articulated elements. The articulation between the various elements is realised with parallel pivots so that relative movements between the single elements are limited to rotations around said pivots. These pivots are reciprocally connected by means of two series of joint links, each of which joint links connects two pivots located consecutively along the track and is equipped to be fitted, at one of its ends, directly and immovably on one of the two pivots, and at its other end, also directly and immovably, on a bushing rotatably coupled on the other pivot. Thus each articulation comprises one pivot, on which a bushing is coaxially and rotatably coupled, which bushing is in its turn axially held, with respect to the pivot, by two joint links stably fixed on the two opposing ends of the same pivot. The two ends of the joint links comprising the successive ring of the articulated chain are coupled on the bushing. The coupling of the two joint links to the two ends of the pivot is normally a press fitting obtained by means of a press. To guarantee the correct functioning of the articulation it is necessary, at the end of the operation, to obtain a determined tolerance between the bushing, rotatably coupled on the pivot, or more frequently between the unit comprising said bushing and spacers, also coupled on the pivot, and the two joint links which are fixed to the ends of the pivot.
The situation becomes particularly important when it is necessary to respect a very limited tolerance. This, for example, is the case in articulations of lubricated tracks in which a frontal seal between the bushing and the joint links fixed to the ends of the pivot is envisaged.
In fact, in the prior art, this axial tolerance is uncontrollable. It is determined as a consequence of the pressing operation of the two joint links which are pressed on to the two ends of the pivot by means of a pressing action sufficient either to bring the two joint links to a determinned reciprocal distance under pressure or to bring them into contact with the "pack" of elements which are rotatably coupled on the pivot, exercising a determined pressing force which is very elevated since it is calculated on the basis of the maximum admitted interference. In the first case the tolerance is inevitably variable within a too-wide range (with values up to 1.div.2 mm); in the second case there is frequently the danger of causing the total blockage of the articulation or indeed the breaking of some of the elements of which it is composed, in particular the spacers.
Another way of operating which does not permit of realising the coupling in such a way as to respect a determined tolerance is that of realising the pressing operation using a determined pressure which is made to act upon the various articulations for a predetermined length of time.
The present invention, as characterised in the claims which follow, offers a simple and effective solution to the above-described problem, that of realising a determined tolerance for the articulation element coupling by means of pressfitting.
Further aim of the present invention is to provide a method for the coupling of the articulation elements which method's execution and efficiency are not minimally influenced by the variability of the number of elements to be coupled within the respective tolerance ranges.
An advantage of the invention is that it permits of reaching an elevated standard of quality and constancy of quality in the realisation of the track articulation mounting operation.
Further advantage lies in the intrinsic ability of the method to provide, in real time from the moment of the mounting operation, important information regarding any possible defect in the coupling and in the parts comprised in the coupling.